The invention arose from a problem in coaching swimmers. A swimming coach watches his swimmers from a pool surround and yells his instructions. Swimming pools especially when indoors are noisy places and it is difficult for any swimmer to understand the shouted instructions. Normally there are many swimmers being coached at the same time and thus each swimmer has to listen for any instruction which might be meant for him and ignore instructions meant for any one else; this is distracting to the swimmer.
The invention is not however limited to swimming instruction but is applicable to most sports and other communication.
The present invention aims to provide a communication system for the transmission of instructions from an instructor to a class or other group of instructees.